When PLAY_LANG is set; treat it as first accepted lang.
When PLAY_LANG is set; treat it as first accepted lang.

Instead of blindly taking the PLAY_LANG value into lang(),
we treat it as the most prioritary language for the user.
This way a user cannot set a language that is undefined for
the application.

marcospereira/playframework,zaneli/playframework,aradchykov/playframework,rajeshpg/playframework,benmccann/playframework,playframework/playframework,hagl/playframework,richdougherty/playframework,richdougherty/playframework,benmccann/playframework,marcospereira/playframework,Shruti9520/playframework,ktoso/playframework,hagl/playframework,playframework/playframework,Shruti9520/playframework,aradchykov/playframework,wsargent/playframework,playframework/playframework,wsargent/playframework,wsargent/playframework,ktoso/playframework,wsargent/playframework,marcospereira/playframework,ktoso/playframework,benmccann/playframework,wegtam/playframework,mkurz/playframework,rajeshpg/playframework,zaneli/playframework,wegtam/playframework,Shenker93/playframework,zaneli/playframework,Shruti9520/playframework,rajeshpg/playframework,rajeshpg/playframework,hagl/playframework,mkurz/playframework,Shenker93/playframework,benmccann/playframework,marcospereira/playframework,Shruti9520/playframework,wegtam/playframework,mkurz/playframework,Shenker93/playframework,zaneli/playframework,richdougherty/playframework,ktoso/playframework,aradchykov/playframework,hagl/playframework,Shenker93/playframework,aradchykov/playframework,wegtam/playframework,richdougherty/playframework,mkurz/playframework